very hot in outer portion of thermosphere
CAUSE:
Chlorofluorocarbons (CFC’s)
Chlorine and bromine
molecules are converted
to more active forms on
Polar Stratospheric Clouds
PSCs form within the
POLAR VORTEX
http://www.cfm.brown.edu/people/sean/Vortex/
Where do the aerosols come from?
http://www.atm.ch.cam.ac.uk/tour/part3.html
Why ?
Ozone depletion
Tropospheric [CO2] increases
Global
Atmospheric
Circulation
Hadley cells: air rises
at equator, falls at 30º
latitude.
Ferrel cells: air falls
at 30º, rises at 60º.
Polar cells: air rises
at 60º, falls at 90º.
Polar Easterlies
Polar Easterlies
Natural Sources of Air Pollution
dust storms
volcanoes
fires
Figure 11.11
•Acids are neutralized in soils with available bases
•Canadian Shield severely affected in central and eastern Canada
Acidity of Rainfall in New Hampshire

2NO + O2  2NO2
NO2 + sunlight  NO + O
O + O2  O3
CH4 + OH  CH3 + H2O
CH3 + O2  CH3O2
CH3O2 + NO  CH3O + NO2
CH3O + O2  H2CO + HO2
H2CO  HCO + H
HCO + O2  CO + HO2
H + O2  HO2
CO + OH  H + CO2
H + O2  HO2
Peroxy radicals can re-oxidize
NO to NO2
O3
-bronchial constriction
-respiratory irritation
-eye irritation
-decreased crop yields
-retards plant growth
-damages plastics, rubber
-odour
VOCs
- eye irritation
-respiratory irritation
-some are natural (terpenes)
-some are carcinogenic
NO2
-decreased visibility
-heart and lung problems
-suppressed plant growth
-decreased infection resistance
-may encourage cancer spread
NO2 + R  peroxyacetyl nitrates
-high toxicity to plants
-respiratory irritation
-damaging to proteins
-eye irritation
CO / SO2 / NO2
• Carbon monoxide (CO) = colorless, odorless gas. From
vehicle exhaust and other sources. Dangerous; prevents
oxygen uptake.
• Sulfur dioxide (SO2) = colorless gas. From coal burning
for electricity and industry. Contributes to acid
precipitation.
• Nitrogen dioxide (NO2) = foul-smelling red gas. From
vehicle exhaust, industry, electricity. Contributes to smog
and acid precipitation.
O3 / Pb / Particulate Matter
• Tropospheric ozone (O3) = colorless gas. Secondary
pollutant from sunlight, heat, nitrogen oxides (NOx),
and C-containing chemicals. Contributes to smog;
harmful to living tissues.
• Lead (Pb) = metal in atmosphere as particulate. From
gasoline additive, phased out in 1980s. Diverse health
impacts, all bad, including effects on young minds.
• Particulate matter = any solid (or liquid) particles
small enough to be carried aloft in air. Dust, soot,
sulfates, nitrates. Causes respiratory damage.
Milankovitch Cycles
Variation of
Earth’s tilt
Variation of
Earth’s orbit
Wobble of
Earth’s axis
Figure 12.3
Source: IPCC
Source: IPCC
Ice core data
Temperature,
CO2 and CH4
are all in
phase
Are the gas
concentrations
a cause or an
effect of
warming or
both ?
1. Reduced Biodiversity
(rapid change)
2. Sea level rise and coastal flooding
(melting ice and thermal expansion)
3. Expansion of tropical disease range
4. Soil Moisture Decreases and
Desertification ?
5. Increased frequency of heat illness
(problem for the elderly)
6. Increased frequency of severe events?
7. Engineering problem of thermokarst
(transportation and housing)
8. Affect on outdoor winter recreation
and winter tourism
1. Increasing NPP
2. Increased food production?: CO2
fertilization, range & growing season
(depends on soil moisture/depth/nutrients)
3. Increased water-use efficiency by
higher plants
3. Increased nutrient-use efficiency
4. High latitude warming
(positive and negative)
IPCC Scenarios for CO2 emissions
The scenario chosen affects model output
Canadian Climate Centre
General Circulation Model
output vs. scenario
http://www.cccma.bc.ec.gc.ca/models/cgcm2.shtml
Model
Output
http://www.cccma.bc.ec.gc.ca/models/cgcm2.shtml
HADCM3 Model Prediction
Global Circulation Model Projection:
Non-uniform spatial distribution of
global surface temperature increase
Testing performance vs. observations
Source: IPCC
What happens if this
circulation shuts down?
Source: IPCC
Source: IPCC
Free Air Carbon Dioxide Enrichment (FACE)
FACE Results:
NPP increases
(eg. 40% in cotton; 25%
for Sweetgum for 550
ppm vs. 370 ppm)
Carbon sink increase limited for forests: Increase in wood
production is short-lived; C goes mainly to fine roots and
leaves; affected by soil fertility
No effect on LAI
Stomatal conductance decreases (increased water-use
efficiency)
Lower leaf nitrogen concentration: need less or have less?
Carbon Sinks
Source: IPCC
Interannual climatic variability at
the global scale
Caused by changing atmospheric and
oceanic circulation in the tropical
Pacific Ocean
Top La Nina December 1998; Middle Normal December
1993; Bottom El Nino Dec 1997
See http://www.cdc.noaa.gov/map/clim/sst_olr/sst_anim.shtml
Evidence of extreme events
or related to population
and human impacts on
natural environments?
Will ‘extreme’ events become more common?
2 hours after the Lethbridge tornado